For people with sight, the landscape can be considered and remembered
as a series of views; a network of prospects. If this is true, then
design of the built environment, decisions of where to build or to
demolish or to leave areas alone, might consider the effects upon
views and visibility. This page demonstrates several capabilities,
issues and options for modeling visibility in GIS. This demonstration
was carried out using ArcGIS Version 8.3.

Lets suppose that the owners of a large cranberry processing
factory are interestrd in enhancing the image of their factory
grounds. As part of an overall landscape enhancement, a historic
plaque is to be placed along the road above the plant, where motorists
can stop and read about the history of the cranberry factory while
looking down on the historic site. How can GIS help to evaluate
and design this overlook?

Viewpoint:
A shapefile is created to represent the x aand y location of the overlook on the
road above the plant.

WIth these data resources, a GIS -- in this case, ArcGIS, can calculate the intervisibility
between each cell in the elevation model and our observer station. Options are available
for setting the height of the observer, and the height of the objects being looked at.
These options create a fairly relaistic model of visibility, unless we want to consider
the interference of vegetation.

If we want to be realistic, we should consider that tall vegetation, and potentially
other things such as buildings may interefere with visibility. We can work this into
our model by adding the height of the vegetation to the elevation surface. Because
the vegetation map does not include roads, our construction of a egetation-height-offset
layer should be merged with a layer of road cells, having an offset of zero.